Light-sensitive layers of n-monoarylhydroxylamines and their nitrones and process of printing thereon



. photographic prints.

Patented Sept. 2, 1947 LIGHT- SENSITIVE LAYERS F N-MONO- ARYLHYDROXYLAMINES AND THEIR NI- TRONES AND PROCESS OF PRINTING THEREON David Malcolm McQueen, Newark, Del., assignor to E. I. du Pont de Nemours & Company, Wilmington, DeL, a corporation of Delaware No Drawing. Application May 9, 1944, Serial No. 534,801

7 Claims.

This invention relates to' photography. More particularly, it relates to light-sensitive elements for obtaining direct prints. Still more particularly, it relates to photographic elements which contain light-sensitive N monoarylhydroxylamines and their nitrones and to processes of obtaining prints therefrom.

Various light-sensitive materials have been used for the preparation of photographic images or prints. A widely used photographic printing material, however, has as the light-sensitive component a photographic silver halide emulsion in a colloid layer. These elements are exposed to an object and then developed in a developer solution and finally the undeveloped silver salts are removed, leaving a negative metallic silver image. Other light-sensitive elements have utilized the light-sensitive dichromates and light-sensitive diazonium salts. The latter materials, after ex,- posure to an image, are developed by treatment with a basic solution of a coupling component such as a naphthol. In the latter case, however, a positive image results since the diazo compound is destroyed in the exposed areas and rendered incapable of coupling. The above described photographic elements, while very useful, have some disadvantages. In the first place, the light-sensitive silver halides are quite expensive. The lightsensitive dichromates result in images of somewhat inferior quality and require a rather tedious processing.

An object of this invention is to supply a new type of photographic material which is free from the disadvantages of the previously proposed materials. A further object is to provide an economical photographic printing element. Another object is to provide a new method of producing Still other objects are to provide a new use for N-monoarylhydroxylamines and their nitrones and to provide a general advance in the art of photography.

The above objects are attained by the preparation and use of photographic elements which have a radiation-sensitive layer composed of an N-monoarylhydroxylamine or a nitrone thereof. The elements may be prepared by coating a support with a thin layer of an N-monoarylhydroxylamine or a nitrone thereof dispersed in a hydrophilic colloid medium. For example, an N-monoarylhydroxylamine, e. g., N-phenyl, N-p-toly1, or N -alpha-naphthylhyroxylamine, or a nitrone thereof, is incorporated in an aqueous solution of a water-permeable colloid such as gelatin and coated on to a support such as paper, metal, glass, or a transparent film base such as a cellulose derivative or a synthetic resin or a superpolymer, e. g., nylon. The N-monoarylhydroxylamines are 7 prepared and coated in the absence of actinic radiations.

The element containing the N-monoarylhydroxylamine or nitrone is exposed through a photographic element containing an image by means of actinic light whereby there is formed in the first named element an image which has a density gradation complementary to the image in the second element. The image formed may be fixed by simply removing the undeveloped portion by washing in a solvent for the hydroxylamine or nitrone, e. g., an aqueous solution.

Th N-monoarylhydroxylamines and their nitrones are especially sensitive to ultraviolet light and it is preferable to use as a source of actinic light a source which is rich in wave lengths of light in the ultraviolet light region of the spectrum. Suitable sources include sunlight, arc lights, including carbon arcs and metal or metal salt-cored carbon arcs, mercury .vapor lamps, rare gas lamps, and fluorescent lamps. V

The nitrones comprehended by the invention are the condensation products of N-monoarylhydroxylamines with aldehydes and ketones. The condensation apparently takes place in accordance with the equation:

In this equation R1 and R2 are hydrogen or a hydrocarbon radical which may be aliphatic, aromatic, aliphatic-aromatic, cyclo-aliphatic, or a heterocyclic radical and Ar is an aryl group. The nitrones have greater chemical stability than the N-monoarylhydroxylamines.

The invention will be further illustrated, but is not intended to be limited, by the following examples wherein the parts are by weight unless otherwise indicated and all procedures prior to exposure are carried out in the absence of actinic light:

. Example 1 A solution of one part of N-alpha-naphthylhydroxylamine in 10 parts of methanol is coated on paper and allowed to dry. The resulting lightsensitive element is exposed through a negative photograph with ultraviolet light having wave lengths from 3000 to 4000 A. for a period of seconds, whereby a red positive image appears on the surface of the coated paper. The resulting print is Washed in the water to remove the unexposed and colorless material and a red positive image having gradations complementary to that of the negative photograph is obtained.

Example 2 A solution tnntei'iiine one ait on N-ilia'ha naphthylhydroxylamine in 10 parts of methanol was added to a solution of 10 parts of gelatin-in" 90 parts of water containing about 0.05;-parts of colorless materials, whereby a red -po"sitiv'e-=pictu' re 7 image results which has gradations complementary to the silver image of the original negative. Example 3 .inanee raef r anae a is ample is sulos'titutedfone part of N-pi-tolylhY- 'drokylamin'e and 'a'phfitographic'eleinint made and processed in the same manner. Awenow image "is formed. p

mattered V eelut on d m feef s ief e' 5. Nmri r e q e i iai esibrfe e de siew h N- -tely hy yl ei e .j 'n 9 baits f methaeelrw e ziseei be ei f 'e'q ffi fi r a e 'a ad iee-M eme tx q l fi a qt fi i .elee etf n h i ture im'age in the form of metallic silver for 61) seconds to the ultraviolet ligfitbfa mercury arc wne v, il1 t 1 f i i h Th ape was "was ed in 'a'olutic'in'of whitewater to remove the unexposed colorlsshitfori'e.

Ex'aiizpleh A soidtionoi S oieigi ia iifen N- i eii imeme (obtained hyfco'fidens'ir'i'g -plienylhy uroxylai'nir e' wi h'peri'zamehyde) in "150 was i ethanol is abated 'iitaan-eiaaque base'and thenf'dried',fA plfotogf c eien en containin a negativepicture imag placed he paper 'e in i t die b s f ne' ftrav e j h "ii mercu'ryarc for G'Os'eConfdsQWHereDy aye ow brown positive image i formed. After" washing the 'pa'perin warm water a yellow hrown picture remains which has gradations complementary to that in the original negative.

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amines A. V H may be substituted other or s T1 N-xen iiiyemyiamme, "N beta riaphthylliydriiicarylhydroiyla me 7 one any team "product's which' have a'wiae "rangeof'sensitivity' to light.

' sensitive nitrones.

For example, alpha-phenyl-Npheny1nitrone is sensitive only to wave lengths of light below about 3009 A., wherea alpha-furyl lI-phenylnitrone has a sensitivity extending i into the visible siaectrum. on the other hand, the 'N-moiio'ai'ylhydroxylamines appear to be somewhat more sensitive to actinic light than their nitrones. The nitrones need not be preformed but can be formed in situ. Thus a mixture of N-hydroxylamines and aldehydeor ketone of the types herein disclosed can "be separately incorporated in the light-sensitive layers, or in the coating compositrons just prior to heating.

A wi'de'vari'e'tyfo f a-ldehydic and ketonic compounds (ketaldones) may be reacted with the '-N-m'onoarylhydroxylamines to produce the light- Among the useful aldehydes are -benzaldehyde, p-tolualdehyde, cinnamaldehyde, furfural, benzaldehyde-o-sodium sulfonate, sodium phthalalde hydate, sodium glyoxylate, 'o chlorobenz'al dehyde, phenylace'taldehyde, 'a'cetdehyde. Suitable ket'oni'c comp unds inclride acetone, methyl "ethyl ketone, die'th'yl 'ketoi'ie,

"diamyl ketone, methyl hflo'utyl 'ke'tone, acetaplienone, le'vulinic "acid, 1 sddium l evuli'nate thyl acetoacetate, ketobutano'l, fr'nethyl viny-l ketorie, and benzophenon'e. Aldhydesaifd ketoneswhich contain the group m l ll,

C=C' are preferred, 'sincethe resultihg 'co'r'ripounds are more s'fisit'lv'eto'uit lavioltligll't.

Variations in'th'e directive wave length of the elements can. 'beobtainddoy varyingthep'articular hydroxyl'amirieor it' 'nitroiie used. Ihus, N alphahydroxylnaphtlfiylamine "is sensitive lo'nger'wave lengths than N p-tolylhydroiiylaniihe which is, in mm, 'airect'eu by light which is or longer wave length than that'fto' which N pher'iylhydroxylamine is'sensitive. Mixtures ieifithe coinpoun'ds can be 'employed, thus resulting "inn product which is senSiti'X/fejoVer a fairly wide range of wave length fof light, I

The N-monoarylhydroizylamines and theirrji'itron'es' can be made in'to photographic iayersby applying them iromfsolutions in vaiioushrgahic sqiveias for water -d p"er bn's, ractice-11 any organ "solvent ma be em loyed ireiiariiig the solutions, so 'ldn'ga s it dos notf actwith the N-monoarylhydroxylamines or hi'tio'jries. Useful solvents includealcohols "of "'1 to =4 "carbon atoms, e, g.,*niethariol,'fethanol, sop're banolgbu- 'tan'ol; glycols, e. g ethyl'ene elven-mar tim glycol; ethers, e e; d idiian'e ethylene "glycol monoethyl ethe r, diethyl'en'e glyccil "monomethfl ether; 'estersgs'uchfas ethyl acetate, inethylfaioe tate, etc. hydrocarbdns, e. g. 5 hei'iariehfliptariephen h rdene -recap thalene, cycl'ohir ane, benzene, o tl-io-inti- "and paraaizyle'ries, ethyl benzene, *inesity-l'erre, "chloroidrfr'n, "ethylene dichloride, trichll oedhylerie etc. his preferred to use "water miscible solvents, however, *suchtile alooi-iols-ofjl to e cltfifiit'olfris- I e we ernew tions or dispersions may be coated onto any type of support, as described above, and dried. In general, it is preferred to have the compounds dispersed in a colloid layer because they are more stable and can be stored at elevated temperatures for several weeks without suffering any loss of sensitivity. Gelatin in particularhas a stabilizing'influ ence upon the compounds. In general, from 0.001 to 0.1 part of the N-monoarylhydroxylamine or nitrone should be used per part of gelatinrjLayersof various thicknesses can be .used but, for most purposes, thicknesses of from one to ten microns are suitable. It is not necessary that the colloid layer be highly permeable to water since cellulose esters, e. g., cellulose acetate and vinyl resins, e. g., polyvinyl acetate, can be used.

The nature of the reaction which takes place when the compounds are exposed to actinic light is not fully understood. It is believed, however, that v the images produced upon exposure (a) of the N monoarylhydroxylamines and (b) the N-arylnitrones are symmetrical azo dyes in accordance with the following exemplary respective equa- NHOH 2 light light I T=HC ample, a layer containing three nitrones capable of giving yellow, magenta and blue-green azo dyes could be printed with three separation negatives successively, in register, limiting the printing light to that portion of the spectrum to which only the desired nitrone is sensitive.

The compounds differ in the speed with which image formation takes place and this fact may sometimes be advantageous. For example, the benzaldehyde and furfuraldehyde derivatives of N-phenylhydroxylamine are much more rapidly decomposed by ultraviolet light than the salicylaldehyde and the cinnamaldehyde reaction products.

The light-sensitive elements of this invention may be used in many types of copying processes since exposure through a negative yields a positive image in the new element, which may be used for the preparation of proofs or as permanent photographic prints. Their ease of processing to colored images makes them especially applicable to the reproduction of line drawings, charts, etc., as an improvement over photostating or blueprinting from papers, etc., and in the production of templates.

As many apparently widely different embodiments of this invention may be made without departingirom the spirit and scope thereof, it is to beunderstoo'dthat the invention is not limited to the specific embodiments thereof except as defined in the appended claims.

LWhatis claimed is: 7

- '1. A radiation sensitive element comprising a support bearing a water-permeable colloidlayer containing an N-arylnitrone. .7

2. A radiation-sensitive element comprising a support bearing a water-permeable colloid layer containing at least one compound taken from the group consisting of N-monoarylhydroxylamines of the formula ArN'I-IOH and their nitrones of the formula V R1R o=N- -Ar r I wherein Ar is a monovalent aromatic hydrocarbon nucleus and R1 and R2 are taken from the group consisting of hydrogen and monovalent hydrocarbon radicals.

3. A radiation-sensitive element comprising a support bearing a gelatin layer containing at least one compound taken from the group consisting of N-monoarylhydroxylamines of the formula ArNHOI-I and their nitrones of the formula wherein Ar is a monovalent aromatic hydrocarbon nucleus and R1 and R2 are taken from the group consisting of hydrogen and monovalvent hydrocarbon radicals.

4. A radiation-sensitive element comprising a paper support bearing a layer of gelatin containing N-alpha-naphthylhydroxylamine of the formula:

NHOH

5. The process which comprises printing a photographic image by means of light rays onto a radiation-sensitive element comprising a, support bearing a thin layer of a compound taken from the group consisting of N-monoarylh'ydroxylamines of the formula ArNHOI-I and their nitrones of the formula wherein Ar is a monovalent aromatic hydrocarbon nucleus and R1 and R2 are taken from the group consisting of hydrogen and monovalent hydrocarbon radicals, and washing the undeveloped colorless compound just recited from the layer with an aqueous solution.

6. The process which comprises printing a photographic image by means of light rays onto a radiation-sensitive element comprising a paper support bearing a, thin layer of a. compound taken from the group consisting of N-monoarylhydroxylamines of the formula ArNHOH and their nitrones of the formula wherein Ar is a monovalent aromatic hydrocarbon nucleus and R1 and R2 are taken from the group consisting of hydrogen and monovalent hydrocarbon radicals, and washing the undeveloped colorless compound just recited from the layer with an aqueous solution,

"7;; The process whichcnmprises printinga photographi'o image by means. of light rays ontoa radiation-sensitive element comprising a paper support bearing a water-permeable colloid; layer containing a compound takenfn'om the group consisting of N-monoarylhydroxylamines ofthe formmaArNHOI-I and. their nitrones. of the tormula 1 wherein Ar is a monouadent aromatic hydrocarbon nucleus and- R1; andiR'e are taken from the group consisting of hydrogen and monovalent hydrocarbon radicals, and washing the undeveloped colorless compound just recited from the layer with an aqueous solution.

DAVID MALCOLM. Mo QUEEN.

Name Date Och-Wat Mar. 15, 1938 OTHER REFERENCES Hackhs. Chemical Dictionary, second edition, by Hackh and. Grant. Publ. by The Blakiston Company, Philadelphia, 1937; pages. 4313 and 636. (Copy irLDivision '7.)

Nuinber 

